Multichannel radio system and method of radio reception



June 18, 1929. CHAFFEE 1,717,662

MULTICHANNEL RADIO SYSTEM AND METHOD OF RADIO RECEPTION Filed March 31. 1922 4 Sheets-Sheet l svwmwoz 3 4 flbtom June 18, 1929. E. 1.. CHAFFEE ,7 7,

MULTICHANNEL RADIO SYSTEM AND METHOD OF RADIO RECEPTION Filed Mairqh 31. 1922 4 Sheets-Sheet 2 awuemto? 8% mzifi June 18, 1929. E. CHAFFEE 1,717,662

MULTICHANNEL RADIO SYSTEM AND METHOD OF RADIO RECEPTION Filed March 31. 1922 4 Sheets-Sheet 3 ill I I gave "box iim u June 18, 1929. CHAFFEE 1,717,662

MULTICHANNEL RADIO SYSTEM AND METHob OF RADIO RECEPTION Filed March 31. 1922 4 Sheets-Sheet 4 avweutoz Patenteddune 18, 1929.

UNITED STATES 1,717,662 PATENT/OFFICE.P-

EMORY LEON CHAFFEE, or BELMONT, MASSACHUSETTS, essienon "r Joint HAYS HAMMOND, JR. v I

MULTIoHAnNEL RADIO SYSTEM AND METHOD or RADIO RECEPTION.

Application filed March 31, 1922. Serial No. 548539. I

Some of the/objects of the present invention are to provide improved selectivity for methods of and. systems for communiontion employing radiant energy; to provide improved means for'the reception of radiant signals of such type that unauthorized listen mg in may be effectually prevented; to pro vide a system for the transmission of intelligence by Hertzianfwaves over a plurality of channels whereby a'portion of the message may be transmitted over each of the channels so that only receiving stations having receivingapparatus of special character; may receive the complete message; to provide means for producing in connection with all of the channels beat notes of unlike frequencies; and to provide other features which will appear in the following description taken in connection with the accompanying drawing.

Referring to the drawing, I p a Figure 1 showsadiagrammatic representation of a receiving system embodying the invention;

.Fig. 2 shows a modified form of system;

Fi 3 shows still another form of s stem 7 and a Fig. at shows another modification of the invention. I I

In the drawings there is shown so muchof the system oftransmission oifi intelligence by Hertzian waves, or so-called wireless system, as is necessary to an understanding of the invention. It is understood that the sending equipment (not shown) isadapted to impress upon theether a plurality of series of continuous or undamped waves. The message is transmitted by intermittently emitting or interrupting. or by changing the frequency, or modifying any other electrical characteristic, or producing other desired changes inthesescries of waves; and the plurality. series are employed for portions der. For example, one of the seriesor channels may be so modified whenever a dot is to of the message respectively'in sequential orloops being positioned at an angle of substantial ly to the direction from which the radiant energy is expected tobe received. The loop 10lorms part of a closed circuit 12 including an adjustable condenser-.13, resonant to a predetermined frequency; which frequency will be hereinafter represented by the symbolA,

The circuit of the loop 10 is operatively connected to a threeelectrode electron device 1 having a usual heated filament forming a hot cathode for emitting electrons, a plate 18 upon which the electrons impinge, and a grid 19 forcontrolling their passagemThe grid is connected'to the loop '10 so as to be controlled by electrical oscillations flowing therein. I p j j i The loop 11 forms partof a closed circuit 15 in a similar manner. Thecircuit 15includes an adjustablecondenser 16 and isresonant to a secondfrequeney A differing from the first named frequencyA The circuit of'the loop 11 is similarly connected to the grid of a secondJthree-eIectrOde'. electron device'17.

The plate circuits' 'ofthedevices 14L 17 include respectively windings 20and 21 of a transformer 22. Inductivelycoupled. to the windings 20 and21isfa third winding 23' I WlllChlS includediin aresonant circuit2 l having for example a variable condenser- 25 and a winding 26 of a coupling 27 3 The coupling 27 is provided with af'sec ondary winding 30 connected in circuit with the grid-19 of a' three electrode electron device 3 1." Atuning condenser 32'may beprovidedlin'a conventional manner. The output circuit of the 'device 31 may include controlleddevice such as telephone receiver 33, which may also take tlie'form of 'a solenoid or relayto control a moven'nentfor function oi a body such as a torpedo boator other object.

A 'heterodyne of suitable form shown conventionally as an alternatorlO and a trans. former llis applied to a common conductor 42 included in the grid cireuitsof both'de vices 14; and 17. Operation the heterodyne 10 produces j an alternating electromotive force in theconductor l2 and in cooperation with impressed oscillations in the loops 10 and 11 a plurality of series of beats, as Willbe subsequently set forth. 7

In the operation of the receiving system of i Fig. 1, "the frequency oflthe heterodyne 40 is preferably such asto be less thanik and greater than A and to diifer'from said frequencies by unlike amounts respectively.

For example, with afrequency -A =G00,000

. cycles per second, and a frequency A, of

500,000 cycles, the heterodyne 40 may generate an electroniotive force having a frequency of 549,500 cycles per second, giving a beat frequency with A, of 50,500and with A of 49,500. Eachof the devices 14 and 17-produces inits'output circuit a superimposed current of the respective beat frequency, and by means of the coupling 22 currents of the frequencies 50,500 and 49,500 are induced in the circuit. The resonant circuit 24 is madev broadly, resonant to these frequencies. --This may: readily be done since these beat frequencies are relatively close to one another. V

In the case cited byway of example, the heterodyne frequency'is intermediate A, and A and A, and A may then differ from each other by any desired amount, other than that mentioned, But if the heterodyne frequency is greater or. lessthan both A and A then these frequencies should differ by a relatively small amount, such as 1000 cycles per'sec'ond. For example, if A 74,500 and A =7 5,500 alieterodynehaving afrequency of 25,000-will produce primary beatsof of thisfrequency. The beating currents are induced by means. of the coupling27 "into the circuit of-the device 31; The device 31 acting as a rectifier or detector producesin itsloutput circuit a superimposed current of the secondary beat frequency (1000), for controlling the indicator or other. controlled device 33. V

A'modified form of recelving equipment 1 is shown inFigure 2, which differs from Figure 1 in having atuned circuit between the output circuit of device 31 and the 0 device, 33. ,The'j circuit 50 is adjusted'in aw-ell known'manner to be resonant to a fre- 'quency of' substantially 1000 I cycles per second. i

i v In the operation of the system of Figure 2,

the incoming radiant energy is received in the same manner as previously described,

and causes current oscillations having frequencies differing from each other by for] example 1000 cycles per, second to co-exist in the circuit 24. i The heating currents effect the grid of thedevice 31, and there is-produced ,1n the output' circuitof thermionic Tdevice 31, acting as a rectifieror detector, a

superimposed current having the frequency of the secondary, beats, i. e., 1 000 cycles per second. The output circuit is. inductively coupledto the resonant circuit: 50 tuned to ofreceiving loops 10 and 11,closed oscilla tory circuits 12 and 15, electron devices 14 and "17, and a heterodyne 40, 41 as in Figure 1.. I

The plate circuit of the device 14includes an inductance forming a primary winding of a transformer 60,"and the plate circuit of the device 17 includes an inductanceforminga primary Winding of a transformer 61.

The secondary windings of the transformers 60 and 61 are connected in series and are included inthe grid or electron controlling circuitof an electron device 62. i

The plate circuit of the device 62includes an inductance forming a primary winding of a transformer whose secondary winding is in series with an, adjustablecondenser 71 and a primary winding of a transformer 72 to form a closed oscillatory circuit. 73 resonant to substantially only a single frequency of current and partially or wholly prevent-ing the {low ofcurrents of other frequencies. The secondary winding of the transformer 72 is "connected in series with the secondary winding of a transformer 74 and the grid or electron controlling element of an electron device 80, whose plate circuit includes the primary winding of the trans.-

former 74 and an indicating or other con- I trolled device 81.

The windings oft-he transformer 74 are adjustably coupled so that the amount of 7 energy induced from the plate circuit of the device 80,in which the primary winding is included, to the grid circuit in which the secondary winding is included, may be varied. The, frequency of oscillations fed back may be varied by an adjustable condenser 75, of conventional type, in shunt with said windings collectively. A bypass condenser 82 of relatively small capacity provides a path for these oscillations, independent of the indicating device 81, withoutmaterially affecting the sensitiveness of the device 81.

In the operation of the receiving system ofrFi'g. '3 the incoming radiant energy is received in the same manner as described,

it being understood thatthe channels employed may have respectively currents of frequencies of say 500,000 cycles per second and, 600,000 cycles per second impressed thereon; The heterodyne 40'may then be adjusted to produce oscillations of say 537,-

500" and through the agency of rectifying devices 14 and '17 cause primary beatjfre- 7 quencies of say 37,500 and 62,500 cyclesper second in the respective plate circuits. These current'oscillations ex st. independently in vthe circuits of the primary windings of the transformers 60 and 61 and are induced into the clrcuit of the secondary windings and induced electromotive, forces of these frequencies coexist in saidsecondary circuit. The oscillations produce secondary beats of a frequency above audibility, in the example named, 25,000, and these beat electromotive forces act upon the grid of the thermionic device 62, acting as a detector, producing thereby rectified output currents'in the plate circuitthereof. This secondary beat current is passed by theresonant circuits 73 and acts upon the grid of the thermionic device 80. The device is arranged for so-called auto dyne beat reception, the transformer being arranged to feed back a portion of the output current of the device 80 into its grid circuit so that there is produced a second oscillatory current differing in frequency from the secondary beat current existing in the resonant circuit 73. by an amount such that the resulting tertiary beats will actuatethe indicating device 81 to produce an audible tone. Under the conditions cited by way of example the second named oscillatory current may have a frequency of 24,000 per second, thus producing tertiary beats of 1000 per second. In the case cited theheterodyne frequency is intermediate the radio frequencies. As in the case of Figure 1 the heterodyne frequency may be outside of these frequencies. For example the radio frequencies may be 600,000 and 625,000respectively. A heterodyne frequency of 562,- 500 will give primary beat frequencies of 87,500 and 62,500 respectively. These beating with each other will give a secondary beat current of 25,000, and, assuming that the autodyne has a local feed back frequency of 24,000, there will be produced tertiary beats of 1000 cycles persecond. I p

In the modified embodiment shown in Fig. 4. there is provided a pair of receiving loops 10 and 11, closed oscillatory circuits 12 and 15, electron devices 14 and 17 hetero-,

,dyne 40, 11, primary windingsof transformers 60 and 61 asin Fig. 8.

The secondary windings of the transformers 60 and 61 are includedfin independent resonant circuits and 91 respectively, these circuits including primary windings of transforn'iers 941 Qand 95, and suitable con densers 92 and 93 respectively for. tuning said circuits to the respective secondary beat frequencies. flThe secondary windings of the transformers 94 ,and 95 are connected in series and are included'in' the grid or potential gradient varying circuit of an electronv device 62. The output circuit of the thermionic device 62 .is' connected in the same manner as in Fig. 8. i A secondary winding of the transformer-72 is included in the input circuit of an electron emitting device 80 whose output circuit includes an indicating device 81 and a winding of the transformer "'71. By means of this transformer energy is fed baclcto the input circuit and there is thus produced a current adjusted by varying tliecondenser 75 to diiferfroxn the current to which the circuit 73 is resonant by. an

amount within the limits of 'audibility and which may readily actuate the indicating device 81, as in the so-called autodyne reception. I 4

The operation of the embodiment of Fig. 4 is the same as for Fig. 3 with the exception that circuits 90 and '91 being resonant to the Each of the thermionic devices comprises an evacuated bulb, having therein a heated filament forming a hot cathode to emit electrons, a plate anode 18 upon which the electrons lmpinge, and a gr1d19 for controlling the passage of electrons.

Illustrative apparatus and circuits have been shown for the purpose of showing some of the Ways in which the invention may be practised, but it is expressly understood that the scope of the invention is not to be. limitedthereby, reference being had to the appended claims for that purpose.

l/Vhat is claimed is: g

,1. A system for thereception ofradiant energy, including a plurality of receiving devices tuned respectively to frequencies fering from each other by a predetermined amount, a single means for producing with oscillations of each of said frequencies two series of beats differing fromjeach other by a predetermined amount, an indicating device, and meansfor causing said device to be responsive to oscillations having afrequency substantially equal to the difference in frequency of said beats. y g

2. Ina system for thereception of radiant energy, including receivingdevices exposed and responsive to etherwaves, said. devices being tuned respectively tofrequenciesdiffering from each other. by a predetermined amount, means for producing w th received an amount above good audibility, means for detecting said beats to. produce currents of therespective frequencies of the beats, and

means-for combining, detecting and indieating the beat currents. j

3. A system for the reception of radiant energy, including receiving'devices arranged to intercept etherwaves andtuned respectively. to frequencies differingfrom each other. by a predetermined amountymeans forproducinga series of beatswith oscillations of each of said frequencies, said beat frequencies difiering from each other by a relativelysmaller amount, means for detect- -ing said beats to produce currents of the series of beats to produce a current of the,

frequency of said beats, and indicating said current.

4. In a system for the reception of radiant energ ,including receiving devices exposed and responsive to ether waves, said devices being tuned respectively to frequencies differingfrom each other by a predetermined amount, 'means for producing a series of beatswith each of said frequencies, said beat frequencies differing from each other by a relatively smaller amount, means for producing another series of beats by the first named series of beats beating with each other, and a circuit selectively responsive to thelast-named series of beats. I

5. In a system for the reception of a' message through the ether, including receiving devices exposed and responsive to ether waves, said devices being tuned respectively to frequencies differing from each other by a predetermined amount, means for producing a series of beats with each of said frequencies, said beat frequencies differing from each other by a relatively smaller amount,

'means for causin the first-named seriesof beats to beat with each other to produce a third series of beats, means selectively controlled by currents of a frequency substantially equal to the frequency of said third series of beats togive a signal, and means for transmitting oscillations having the fre quency of said third series of beats to said last-mentioned means;

' 6. In a system for thereception of radiant energy, including receivingdevices exposed and responsive to ether waves, said devices being tuned respectivelyto frequencies diffez-ing from each otherby a predetermined amount, means for producing a series of I beats with oscillations of each of said freenergy, including two receiving devices eX-" posed and responsive to ether, waves, said devices belng tuned respectively to frequens uencies means for detectin': said beats to q 1 a: produce currents of the respective f'requencies of the beats, means for combining the beat currents'to produce a third series of beats, and means for detecting and indicat-' ing said third series'of beats;

7. In a systemforthe reception of radiant cies' differingfrom each other by a predetermined amount, means for producing aseries ofbeats with each of said frequencies, said beat frequencies differing from eachother .by a relatively smaller amount, a'netwo'rk infductively coupled to both of said receiving devices, ineansrcontrolled by: said'network means for producing a series of beats with oscillations of each of said frequencies, said beat frequencies differing from each other by a relatively smaller amount, means for causing the first-named series of beats to produce a third series of beats by beating with each other, said last-mentioned means including a network inductively coupled to both of said receiving devices, an indicating device, and means for causing the indicating device to be operated under the control of currents of a frequency substantially equal to thefrequency of said third series of beats.

9. In a system for the reception of radiant energy, including two receiving devices arranged to' intercept ether waves and tuned respectively to frequencies differing from each other by a predetermined amount,

means for producing a series of beats with oscillations of each of said frequencies, said 'beat'frequencies differing from each other by a relatively smaller amount, means for causing the first-named series of beats to produce a third series of beats by beating with each other, said last-mentioned means including a single circuit coupled to both of said receiving devices, an indicating device, and means for causing the indicating device to be operated under the control of currents of a frequency substantially equal 01 the frequency of said third series of eats.

with each of said receiving devices, means for applying to the input circuit of each of SZLlditllGIDllOIllC devices an oscillating current having a frequency differing from each of said first named frequencies by unlike amounts, a resonant circuit tuned to a each of said last named difference frequencies for transmitting currents of said fre-' quencies only, a single. thermioniedevice operatively connected to both of said resonant circuits, 'a resonant circuit connected with the output of said thermionic device and tuned to the beat frequency of the currentstransmitted by said first named resonant circuits fortransmitting oscillating currents of said beat frequency only, and means for detecting and indicating said last named transmitted'current.

10. A system forthereception of radiant ii. A system for the reception of radiant energy including a plurality of closed oscillatory circuits each including a loop aerial, each of said circuits being tuned to frequencies differing from each other by a predetermined amount, a thermionic device operatively connected with each of said tuned circuits, means for applying to the input circuit of each of said thermionic devices an oscillating current having a frequency differing from each of said first named frequencies by unlike amounts, a resonant circuit tuned to each of said last named difference frequencies for transmitting currents of said frequencies only, single thermionic device operatively connected to both of said resonant circuits, a resonant circuit connected with the output of said I thermionic device and tuned to the beat frequency of the currents transmitted by said first named resonant circuits for transmitting oscillating currents of'said beat frequency only, and means for detecting and indicating said last named transmitted current.

12. A system for the reception of radiant energy including a plurality of receiving devices tuned to frequencies differing from each other bya predetermined amount, a thermionic device operatively connected with each of said receiving devices, means for applying to the input circuit of each of said thermionic devices an oscillating current having a frequency differing from each of said first named frequencies by un like amounts, a single thermionic device operatively connected to the output circuit of both of said thermionic devices, a resonant circuit connected with the output of said third thermionic device and tuned to.

the beat frequency of the currents impressed upon said first named receiving devices for transmitting oscillating currents of said beat frequency only, and means for detecting and indicating said lastnamed trans mitted current. y p l 13. A system for the reception of radiant energy including a plurality of closed oscillatory circuits each including'a loop aerial, each of said circuits being tuned to fretuned to the beat frequency of the currents impressed upon said first named circuits for transmitting oscillating currents of saidbeat frequency only, and means for detecting and curindicating said last named transmitte rent. j I i 7 v 1.4. A receiver for radiant energy, including a pluralityofclosed oscillatory circuits each comprising a loop aerial, each of said circuits being tuned to respondto a series of electromagnetic oscillations, said oscillations having frequencies differing from each other bya predetermined amount, means for producing with each of said series of oscillations beat currents of unlike periodicity, a resonant circuit i'esponsive'to each of said beat currents and adapted totransmit a cur-, rent of substantially the respective frequency only, means for permitting currents of said heat frequencies tocoexist' and to produce currents having a secondarybeat frequency substantially equal to the difference between the first namedbeat frequencies, a resonant circuit responsiveto'said secondary beat frequency and adapted to transmit a current of substantially said secondary beat frequency only, means for producing currents differing in frequency from said secondary beat" current to produce tertiary beat frequency current, andsignal ndicating means responsive to'the tertiary beat'current.

15, A receiver for radiant energy includ-' ing a plurality of closed oscillatory circuits each including a loop aerial, each of said circuits being tunedto respond to a series of electromagnetic oscillations, said oscillations having frequencies differing from each other by a predetermined amount, means for producing a current differing in frequency from each of said series of oscillations by unlike ion amounts respectively so as to produce two beat currents of unlike periodicity, a detectoroperatively connected to respond to said beat currents, a resonant circuitcoupled to the output circuit of said detector and tuned to a frequency substantially equal to the difference between i said heat currents and adapted to transmit a'current having a fre quency substantially equal to said differdevice and an autodyne whereby said indicating deviceis responsivetosaid last named current; v I

165A receiver for radiantenergy including aplurality of closed oscillatory circuits each comprising a loop aerial, each of said circuits being, tuned to respond to a series of electromagnetic oscillations, said ,oscillations having frequencies differing from each other by a predeterm ned ainount,means for producing with 6&Cl1'0f said series of oscillations beat currents of unlike periodicity, v

a single circuit for combining saidbeat currents, a detector connected to said circuit, a resonant circuit operatively connected with the output side of the detector and tuned to a secondary heat current having a frequency ence frequency only," and means coupled'to said resonant circuit including an ind cating cal substantially equal to the difference between said first named beat currents, and an indicating device controlled by current transmit- I ted through said resonant circuit.

17; A receiver for radiant energy including a plurality of closed oscillatory circuits each comprising a loop aerial, each of said circuits being tuned to respond to a series of electromagnetic oscillations, said oscillations having frequencies difi'ering from I electromagnetic oscillations, said oscillations having frequencies differing from each other by apredetermined amount, means for pro,- ducing w1th ,each of said series. of oscillations beatcurrents of unlike periodicity, a

resonant circuitresponsive to a secondary beatcurrent having a frequency substantiallygequal to the difference between said first named beat currents and adapted to transmit acurrent of said secondary beat frequency only, a detector' operatively connected with said circuit, and an indicating device responsive to currents transmitted through said resonant circuit. I

jl9. Areceiving systemfor radiant energy including a plurality of tuned receiving circuits adapted to receive electromagnetic .waves of, unlike frequencies respectively, a

detector for each of said circuits, means for applying tosaid detectors an oscillating current having a frequency differing from each of said first named frequencies by unlike amounts, a resonant circuit tuned to each of, said last named CllfiGIQIlCG frequencies and connected operatlvely tosaid detectors for,

transmitting currents of said difference frequencies only, a circuit operatively connected with said resonant circuits and arranged to have impressed thereon currents of said clifference frequencies, and athird resonant circuit tuned to the secondary beat. frequencyof said difference frequencies, a circuitfoperatively connected with said third resonant circuit and arran ed to have iml s b pressed thereon anoscillating current dif 'fering frona saidseoondary beat frequency to'produce a tertiary frequency and indicating device controlled by oscillating currents of said tertiary beat frequency.

'20. A method of receiving radio signals transmitted on a plurality of series of oscillations of different frequencies, which consists -in selectively receiving the series of oscillations, heterodyning said series of oscillations with, locally generated oscillations to produce from the series of oscillations beat currents of different frequencies respectively, and utilizing saidbeat currents to reproduce a signal.

21. A method of receiving radio signals transmitted on a plurality of series of oscillations of different frequencies, which consists in selectively receiving the series of oscillations, heterodyning all of said series of oscillations with locally generated oscillations of a single frequency such as, to pro-' duce fromthe plurality of series, of oscillations beat currents of different frequencies respectively, combining said heat currents to cause them to produce a third series of boats, and detecting and indicating said third series ofbeats.

22. Almethod of receiving radio signals transmitted on a plurality of series of oscillationsof frequencies di'fferingfrom each other by an amount above good, audibility, which consists in selectively receiving the series of oscillations, heterodyning said series of oscillations with locally generated oscillations to produce from the plurality of series of oscillations beat currents of different frequencies, combining said heat currents to causethem to produce a third series of boats, and detecting and indicating said series of beats. v 23. A method of receivingradio signals transmitted on two series of oscillations of frequencies differing from each other by an amount above good audibility, which consists in selectively receiving the series of oscillations, heterodyning bothrof said series of oscillations with locally generated os,

cillations of a single frequency of such value as to produce from the series of oscillations beat currents of frequencies differing from each other by anainount less than the difference between the frequencies of said series of osc llations, but also above good audibility, combining said beat currents to cause them to produce a third series of beats, detecting said series of beats, heterodyning current oft-he frequency of said third series of beats with locally generated current and indicating the resultant current.

In testimony 'whereof Ihereunto affix my signature.

EMORY LEON CHAFFEE." 

